Switzerland comprises less than 4% of the global stock market, so for most American investors who aren’t currency speculators the surge didn’t directly have a large impact on their portfolios. But it was later revealed that a hedge fund, Everest Capital’s Global Fund, was essentially wiped out by the currency swing. And there were likely a number of other funds that were buffeted as well.

The travails of such funds highlight the importance of knowing what you own in your portfolio. “Knowing what you own” doesn’t mean memorizing the names of all your holdings or learning facts about each one. Instead it means having a high-level understanding of how the different pieces of your portfolio fit together: which asset classes, sectors, and regions of the world your portfolio is exposed to.